1. Field of the Invention
This invention relates to an apparatus for acquiring human finger manipulation data useful for analyzing manipulative motions of the human hand in order to acquire data regarding motion of the human fingers and force acting on the fingertips for application of the data to control of a robot hand. (Except as otherwise obvious from the context, the term xe2x80x9cfingerxe2x80x9dused in this specification includes the thumb).
2. Description of the Prior Art
Conventional devices developed for acquiring data regarding human finger motion include one type consisting of a glove having bending sensors whose resistance value changes with finger joint bending attached by sewing at the back of the finger joints (e.g., Super Glove Jr. marketed by Nissho Electronics Co. and Cyber Glove marketed by Virtual Technologies, Inc.) and another type that uses a parallel-link goniometer straddling the finger joints (e.g., Dextrous Hand Master marketed by EXOS).
For detecting distribution of pressures acting on the fingers and palm of the human hand, there has been developed a glove-like device worn on the fingers that has a distribution-type tactile sensor utilizing a pressure-sensitive conductive rubber or conductive ink sheet material sewn on the glove (e.g., Glove Scan System marketed by Nitta Co.).
Sensors developed for acquiring data regarding forces along six axes include types designed for mounting on the wrist of a robot (e.g., six-axis force sensor IFS series market by Nitta Co.) and types designed for mounting on a fingertip of a robot hand (e.g., NANO sensors marketed by BL Autotech, LTD.).
Analysis of the manipulative actions of the human hand based on acquired human hand grasp/manipulation data provides information that can be used to develop a robot hand grasping and manipulation algorithm that takes advantage of human knowledge and experience. Exploitation of human knowledge and experience opens the way to development of an algorithm for grasping and manipulating paper, cloth, cable and other flexible materials, which has so far been difficult to accomplish.
To achieve such grasping and manipulation it is essential to maintain dynamic balance and dynamic stability in the grasping operation. Since human finger motion data alone is therefore not sufficient, the contact forces acting on the fingertips must also be measured.
Humans manipulate objects chiefly with the fingertips. In acquiring human finger motion data, therefore, the importance of acquiring fingertip motion data far outweighs that of acquiring data regarding the motion of the individual joints.
Devices developed up to now for acquiring data regarding human finger motion include one that consists of an ordinary thin glove having bending sensors whose resistance value changes with finger joint bending attached by sewing at the back of the finger joints (e.g., Super Glove Jr. marketed by Nissho Electronics Co. and Cyber Glove marketed by Virtual Technologies, Inc.). When the wearer bends a finger, the device detects the finger joint angle from change in the resistance of the bending sensor.
A joint angle data detector has been developed which uses a parallel-link goniometer that straddles the finger joints with two sets of parallel links whose one side lies perpendicular to the finger links and whose jointed portions are equipped with angle detectors (Dextrous Hand Master marketed by EXOS).
These devices measure the individual joint angles of the human finger. In order to determine the motion of the fingertip, therefore, a complex calibration is required for calculating the effect length of the finger links.
As a device for detecting human finger tactile force, there has been developed a sensor glove having a distribution-type tactile sensor utilizing a pressure-sensitive conductive rubber or conductive ink sheet material sewn on the glove (Shimojo et al., xe2x80x9cDevelopment of Sensor Glove MKIII for measuring grasping pressure distribution,xe2x80x9d The 14th Science Lecture Meeting of the Robotics Society of Japan, 1996. Also, Glove Scan System marketed by Nitta Co.).
This sensor glove can detect distribution of pressures applied onto the fingers and palm. However, the detected force components are only those in the direction perpendicular to the surface of the sensor. When grasping/manipulating an object, a human being is known to utilize frictional force (tangential to the sensor surface) and moment at the fingertip surface. The sensor glove is therefore inadequate because it cannot detect frictional force tangential to the sensor surface or moment at the sensor surface.
When human hand grasping data are used directly for robot hand control, the data is preferably acquired using the same type of sensor as used by the robot hand. In this regard, it has been reported that as the sensor mounted on the fingertip of the robot hand it is important to use a six-axis force sensor (Nagata et al., xe2x80x9cDevelopment of a Fingertip-type 6D Force Sensor and Error Evaluation of Contact Point Sensing,xe2x80x9d Journal of the Robotics Society of Japan, Vol. 14, No. 8, 1996).
In view of this finding, the sensor used to detect contact force acting on the human finger should preferably be a six-axis force sensor that can be worn on the finger and is able to detect force and moment in three orthogonal directions.
Although six-axis force sensors for robots have been developed, even the smallest, the NANO sensors produced by BL Autotech, Ltd., measure 18 mm in diameter and 32.8 mm in length. Existing six-axis force sensors are therefore too large to be worn on the human fingertip.
In light of the foregoing circumstances, the inventor earlier developed a force sensor worn on the finger comprising a fingerstall for finger insertion, an elastic component and a finger cover for making contact with an object (U.S. patent application Ser. No. 09/610,968). This force sensor detects dynamic variation in contact force when the wearer manipulates an object. However, it is not able to measure three-dimensional motion of the fingers when an object is manipulated.
An object of the present invention is therefore to provide an apparatus for acquiring human finger manipulation data that, by accurately measuring not only fingertip contact force during grasping of an object with the fingertips but also three-dimensional motion of the fingers grasping the object, enables analysis of manipulative motions of the human hand.
To achieve this object, the present invention provides an apparatus for acquiring human finger manipulation data comprising at least one finger motion detector composed essentially of a force sensor capable of being fitted on a human fingertip, at least three links and at least four angle detectors; and a base supporting the finger motion detector, wherein the base is attachable to an external mount or a human hand, the force sensor is fittable on a human finger and connected to the base through a link mechanism constituted by the plurality of links, the at least four angle detectors are attached at pivots between the links constituting the link mechanism and optionally at a pivot between the link mechanism and the base, three-dimensional motion of the finger is determined by measuring data of the angle detectors of the link mechanism, and fingertip contact force is measured by the force sensor.
The angle detectors can be potentiometers, encoders or the like.
Not fewer than one and not more than five finger motion detectors can be supported on the base.
An inclination angle sensor can be installed on the base for measuring inclination of the base relative to vertical.
The base can be attached to a glove to be worn on a human hand.
The apparatus for acquiring human finger manipulation data according to the invention thus enables acquisition of data not only regarding contact forces acting on human fingertips but also regarding three-dimensional motion of the fingers at the time of grasping an object. By using the acquired data to analyze the manipulative actions of the human hand it becomes possible to develop a robot hand grasping and manipulation algorithm that takes advantage of human knowledge and experience, and by this to enable a robot hand to grasp and manipulate paper, cloth, cable and other flexible materials.
The above and other objects and features of the present invention will become apparent from the accompanying drawings and following detailed description.